scholarly journals THE EFFECT OF CHANGES OF ENVIRONMENT ON THE ELECTRICAL AND IONIC PATTERN OF MUSCLE

1956 ◽  
Vol 40 (2) ◽  
pp. 263-288 ◽  
Author(s):  
F. H. Shaw ◽  
Shirley E. Simon ◽  
B. M. Johnstone ◽  
Mollie E. Holman
Keyword(s):  
Action Potential ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Na Pump ◽  
Straight Line ◽  
Slight Elevation ◽  
The Absolute ◽  
K Concentration ◽  
Toad Bufo ◽  
External K

The resting and action potentials of sartorius muscles of the toad, Bufo marinus, have been measured under varying conditions of external environment. At the same time, analyses for Na+ and K+ content were carried out. There was a slight elevation of 2 mv. when the measurements were made in phosphate-Ringer instead of in bicarbonate-Ringer. The R.P. was independent of the hydrogen ion concentration between pH 6.5 and 8.5, although at these pH's there was marked alteration in the level of Na+ and K+ in the muscle. Alteration of the external K+ level between 0 and 50 m.eq./liter has little influence on the internal K+ concentration. When the log of the external K+ concentration is plotted against the R.P. there is not a linear relationship until the external K+ is raised above 12 m.eq./liter, at which point the cell is unexcitable. Above this value a straight line with a slope of 58 mv. per ten-fold change in concentration is obtained, but the absolute values at any point are about 35 per cent higher than those which would be given by the Nernst equation. Alteration of the external Na+ level within a range of 45 to 650 m.eq./liter resulted in marked changes in the internal Na+ content, without, however, having any effect on the ratio Na+out/Na+in. This ratio has remained at about 3 in spite of marked fluctuations in the absolute value of the internal and external Na+ levels. When the Na+ level is lowered there is a decrease in the height of the action potential although there is no alteration in the ratio Na+out/Na+in. As the Na+ level is raised the height of the action potential is not affected even in the presence of a fivefold increase in Na+ in the Ringer. The results do not support the conclusion that the bioelectric potentials can be calculated from the ionic ratios by means of simple physical chemical hypotheses such as the Nernst or Goldman equations. The maintenance of the normal K+ content of the cell cannot be accounted for by a Donnan mechanism. No definite evidence has been produced to explain the mechanism of a Na+ "pump." In other words, the concept of a Na+ pump requires that there shall be a physico- or organochemical mechanism which will distinguish between Na+ and K+ (or other) ions. There is evidence that Na+ can be extruded against a concentration gradient. On the other hand the cell is able to maintain a constant ratio of external to internal Na+ even when the cell has been severely damaged by very high external Na+ levels.

The effects of sodium pump activity on the slow inward current in sheep cardiac Purkinje fibres

1982 ◽  
Vol 214 (1195) ◽  
pp. 249-262 ◽  
Keyword(s):  
Ion Concentration ◽  
Slow Inward Current ◽  
Purkinje Fibres ◽  
Inward Current ◽  
Na Pump ◽  
Pump Activity ◽  
External Site ◽  
K Concentration ◽  
Low K ◽  
Cardiac Purkinje Fibres

The effects of Na pump activity on the slow inward current, I si , magnitude and twitch tension were investigated in sheep cardiac Purkinje fibres. A two-microelectrode voltage-clamp method was used, tension being measured simultaneously. Na pump activity was lowered either by reducing the extracellular K concentration, [K] o , or by applying the cardiotonic steroid strophanthidin. Reduction of [K] o from 4 to 0 mM leads to time-dependent increases in I si magnitude and twitch tension. The increases of I si and tension could be reversed by adding Tl, Rb, Cs or NH 4 ions to the K-free superfusate. The actions of these ions are attributed to the known ability of these cations to activate the external site of the Na pump. This conclusion is supported by the observation that such activator cations do not reverse the increases in I si and tension produced by strophanthidin. We conclude that the effects of low [K] o on I si are mediated by Na pump inhibition. Similarly the Na pump inhibition produced by strophanthidin increases I si and tension, although, in this case, other mechanisms may also contribute. Measurements of the activity of the electrogenic Na pump show that elevated intracellular Na ion concentration secondary to Na pump inhibition and not the instantaneous Na pump turnover rate mediates the increase in I si magnitude.

The α-action of catecholamines on the guinea-pig taenia coli in K-free and Na-free solution and in the presence of ouabain

1977 ◽  
Vol 197 (1128) ◽  
pp. 255-269 ◽  
Keyword(s):  
Guinea Pig ◽  
Prolonged Exposure ◽  
Membrane Conductance ◽  
Membrane Resistance ◽  
Equilibrium Potential ◽  
Taenia Coli ◽  
Free Solution ◽  
Na Pump ◽  
K Concentration ◽  
External K

The responses of guinea-pig taenia coli to the α-action of adrenaline and noradrenaline, recorded with the double sucrose-gap method, were ( a ) studied in conditions which inhibit Na-pump activity (exposure to 0 K, 0 Na, ouabain, low temperature) and ( b ) compared with the effect of Na-pump activation (readmission of K after prolonged exposure to 0 K). When the external K concentration was modified, the alteration of the change in membrane potential produced by the catecholamines was as would be expected from the shift of the K-equilibrium potential. The decrease in the membrane resistance was greater in a high external K con­centration and smaller in K-free solution. Readmission of K after prolonged exposure to K-free solution produced a large hyperpolarization, but, in the presence of ouabain (5 × 10 -5 M) or in the absence of Na, K readmission produced depolarization. In contrast, the effects of adrenaline and noradrenaline were not essentially modified by ouabain, nor by removal of Na. Reduction of the external K concentration enhanced the hyperpolarization by catecholamines even in the presence of ouabain or in the absence of external Na. During prolonged exposure to adrenaline or noradrenaline (7min) the increase in membrane conductance and the hyperpolarization of the membrane were largely maintained, though there was some spontaneous recovery in the presence of the catecholamines. These long-lasting respon­ses were essentially the same when the temperature was lowered from 37 to 20°C, and also in the presence of ouabain. All the results obtained were unaffected by the presence or absence of propranolol. It was concluded that the hyperpolarization produced by the α-action of catecholamines did not involve an activation of the Na-pump but was mainly caused by an increase in the K conductance of the membrane.

The Hydrogen-Ion Concentration of Natural Waters I. The Relation of pH to the Pressure of Carbon Dioxide

1926 ◽  
Vol 4 (1) ◽  
pp. 46-72
Author(s):  
J. T. SAUNDERS
Keyword(s):  
Carbon Dioxide ◽  
Slow Rate ◽  
Natural Waters ◽  
Great Accuracy ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Normal Concentration ◽  
Straight Line ◽  
Hasselbalch Equation

1. The Henderson-Hasselbalch equation is shown to be entirely applicable to natural waters. 2. The value of pK1' is dependent on the normal concentration of the metallic kations present in the solution, including those derived from any neutral salts. The relation between pK1' and this concentration can be represented by a straight line for concentrations up to 1.0 normal. The equation which expresses this relation is pK1' = 6.52 - 0.53 3√c,where c is the normal concentration of metallic kations. 3. Methods for measuring accurately the pH by colorimetric methods are given. From the pH thus measured the pressure of carbon dioxide with which the solution is in equilibrium can be calculated with great accuracy. 4. By combining the results obtained the pH (corrected, if necessary for salt error by the curve on p. 56) of a solution of bicarbonates of normal concentration (Bik) as determined by the method described on p. 51, is related to the pressure of CO2 in mm. Hg (pCO2 with which the solution is in equilibrium by the equation pH = 10.70 - 0.53 8√c + log Bik/pCO2. 5. Bicarbonates are transformed into carbonates at a very slow rate when the pressure of carbon dioxide in the solution is reduced. The slow rate at which this process occurs accounts for many natural waters having larger amounts of calcium and magnesium bicarbonates held in solution than can be accounted for by the pressure of carbon dioxide with which the solution is in equilibrium.

INVESTIGATION OF BEE BREAD AND DEVELOPMENT OF ITS DOSAGE FORMS

2014 ◽  
Vol 21 (1) ◽  
pp. 16-22 ◽  
Author(s):  
Ilze Barene ◽  
Irena Daberte ◽  
Sanita Siksna
Keyword(s):  
Thin Layer ◽  
Thin Layer Chromatography ◽  
Potato Starch ◽  
Microscopic Analysis ◽  
Stability Study ◽  
Ion Concentration ◽  
Wet Granulation ◽  
Hydrogen Ion Concentration ◽  
Bee Bread ◽  
Layer Chromatography

The aim of the study. The objective of this study was to investigate microscopic, physical and chemical properties of bee bread collected in three regions of Latvia in order to compare the quality and to investigate the possibility of producing granules containing bee bread. Material and methods. Microscopic analysis of bee bread samples was performed. Plant herbaria, special literature and internet sources were used for identification of pollen. Thin layer chromatography was used for identification of carotenoids and flavonoids. Granules were prepared by wet granulation method. Lactose, calcium lactate, calcium carbonate, potato starch and purified water were used as excipients. Appearance, loss on drying, pH of aqueous solution and content of carotenes were estimated. Results. Microscopic analysis showed mostly native pollen identified as willow pollen. Beta-carotene identified and 2 carotenoids found by thin layer chromatography. Two zones of flavonoids found on chromatograms at day light and 6 zones at ultra violet light. The comparison of bee bread samples of 3 regions of Latvia showed insignificant differences in appearance and consistency, hydrogen ion concentration 3.93–4.23, loss on drying 7.72–11.07 %; content of carotenes calculated to bcarotene 6.77–9.35 mg%. Stability study of bee bread samples showed greater changes after storage at 40ºC temperature. All compositions of granules showed appropriate appearance and flowability. Quality of granules: loss on drying 5.48–13.5%, content of carotenes calculated to b-carotene 5.77–6.75 mg%. Conclusions. Pollen of willow can be considered as an indicator of the origin of bee bread in Latvia. Bee bread samples of three regions of Latvia have insignificant differences in physical, chemical parameters.

Hydro-geochemical properties with respect to landuse in the southernmost river of Kerala

2018 ◽  
Vol 6 (1) ◽  
Author(s):  
Badusha M. ◽  
Santhosh S
Keyword(s):  
Organic Carbon ◽  
Drainage Basin ◽  
Anthropogenic Activities ◽  
Oxygen Demand ◽  
Ion Concentration ◽  
Total Hardness ◽  
Hydrogen Ion Concentration ◽  
Geochemical Properties ◽  
Quality Of Water

The hydro geochemical features of Neyyar River for a period of one year from May 2015 to April 2016 were analyzed. Six sampling sites were fixed considering physiography and present landuse pattern of the river basin. The residents in the drainage basin are primarily responsible for framing a better landuse and thereby maintain a good water and sediment regime. Geospatial pattern of the present landuse of the study area indicated that the sustainability of this river ecosystem is in danger due to unscientific landuse practices, which is reflected in the river quality as well. The parameters such as hydrogen ion concentration, electrical conductivity, chloride, Biological Oxygen Demand, total hardness and sulphate of river water and Organic Carbon of river bed sediments were analyzed in this study. The overall analysis shows that the highland areas are characterized by better quality of water together with low organic carbon, which is mainly due to better landuse and minimal reclamation. The midland and lowland areas are characterized by poor quality of water with high organic carbon, which is due to high anthropogenic activities and maximum pollutants associated with the region together with the alteration in landuse from a traditional eco-friendly pattern to a severely polluted current pattern.

EFFECTS OF SOIL ACIDITY ON RHIZOBIA NUMBERS, NODULATION AND NITROGEN FIXATION BY ALFALFA AND RED CLOVER

1977 ◽  
Vol 57 (2) ◽  
pp. 197-203 ◽  
Author(s):  
W. A. RICE ◽  
D. C. PENNEY ◽  
M. NYBORG
Keyword(s):  
Nitrogen Fixation ◽  
Soil Ph ◽  
Soil Acidity ◽  
Field Experiments ◽  
Rhizobium Meliloti ◽  
Acid Soils ◽  
Red Clover ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Greenhouse Experiments

The effects of soil acidity on nitrogen fixation by alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.) were investigated in field experiments at 28 locations, and in greenhouse experiments using soils from these locations. The pH of the soils (limed and unlimed) varied from 4.5 to 7.2. Rhizobia populations in the soil, nodulation, and relative forage yields (yield without N/yield with N) were measured in both the field and greenhouse experiments. Rhizobium meliloti numbers, nodulation scores, and relative yields of alfalfa decreased sharply as the pH of the soils decreased below 6.0. For soils with pH 6.0 or greater, there was very little effect of pH on any of the above factors for alfalfa. Soil pH in the range studied had no effect on nodulation scores and relative yields of red clover. However, R. trifolii numbers were reduced when the pH of the soil was less than 4.9. These results demonstrate that hydrogen ion concentration is an important factor limiting alfalfa growth on acid soils of Alberta and northeastern British Columbia, but it is less important for red clover. This supports the continued use of measurements of soil pH, as well as plant-available Al and Mn for predicting crop response to lime.

scholarly journals DNA Aptamer Functionalized Hydrogels for Interferometric Fiber-Optic Based Continuous Monitoring of Potassium Ions

Biosensors ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 266
Author(s):  
Nataša Žuržul ◽  
Bjørn Torger Stokke
Keyword(s):  
Conformational Transition ◽  
Polymer Network ◽  
Potassium Ion ◽  
Ion Concentration ◽  
Dna Aptamer ◽  
Blood Levels ◽  
Label Free ◽  
Practical Applications ◽  
Hydrogel Matrix ◽  
K Concentration

In the present paper, we describe a potassium sensor based on DNA-aptamer functionalized hydrogel, that is capable of continuous label-free potassium ion (K+) monitoring with potential for in situ application. A hydrogel attached to the end of an optical fiber is designed with di-oligonucleotides grafted to the polymer network that may serve as network junctions in addition to the covalent crosslinks. Specific affinity toward K+ is based on exploiting a particular aptamer that exhibits conformational transition from single-stranded DNA to G-quadruplex formed by the di-oligonucleotide in the presence of K+. Integration of this aptamer into the hydrogel transforms the K+ specific conformational transition to a K+ concentration dependent deswelling of the hydrogel. High-resolution interferometry monitors changes in extent of swelling at 1 Hz and 2 nm resolution for the hydrogel matrix of 50 µm. The developed hydrogel-based biosensor displayed high selectivity for K+ ions in the concentration range up to 10 mM, in the presence of physiological concentrations of Na+. Additionally, the concentration dependent and selective K+ detection demonstrated in the artificial blood buffer environment, both at room and physiological temperatures, suggests substantial potential for practical applications such as monitoring of potassium ion concentration in blood levels in intensive care medicine.

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